Re: [Discuss-gnuradio] how to deal with "underride"

[Tom Rondeau]

On Wed, Dec 12, 2012 at 6:20 PM, zhengxiangwei <address@hidden> wrote:

I think frequency offset may not be the reason.

The attachment is the oscilloscope picture. The first one use DBPSK modulation, which can be received by simple_trx.py. The second one use GMSK modulation, which can be successfully  received by simple_trx.py.

I wonder is there any reason may cause simple_trx.py fail to work using DBPSK.

Thank you.

 =================================
Xiangwei Zheng

Neither of those figures really shows anything. The bandwidth is way too high. But the fact that the scope is telling you that the signal is clipping might be an indication that you're feeding way too much power into the transmitter.

Tom

 

---

From: address@hidden
Date: Wed, 12 Dec 2012 12:07:31 -0500
Subject: Re: [Discuss-gnuradio] how to deal with "underride"
To: address@hidden
CC: address@hidden

On Wed, Dec 12, 2012 at 11:49 AM, zhengxiangwei <address@hidden> wrote:

I compared the difference when using GMSK and PSK in simple_trx.grc which use radio_hier.grc.

When use GMSK, 

it calls

gr_fir_fff: using SSE

When use PSK,

it calls 

gr_fir_ccf: using SSE

gr_fir_ccc: using SSE

Also I compare with benchmark_tx,

when use PSK

it calls gr_fir_ccf: using SSE

when use gmsk

it calls

gr_fir_fff: using SSE

I know c, f means different data type: complex and float.

Is it the reason why PSK fail to work? which calls additional  "gr_fir_ccc: using SSE"?

If it is not the reason, I will dive into framer, which may also cause failure in TX.

Thank you. 

 =================================
Xiangwei Zheng

No, this is not the reason. This is probably a channel filter used in PSK signals and not in the GMSK signals.

Most likely the reason is frequency offset or too much or too little power.

Tom